The present invention relates to novel prostaglandin analogs. Particularly, these compounds are analogs of the prostaglandins wherein the C-20-C-19 position is unsaturated, i.e., 19,20-didehydro-PG compounds. Most particularly, the present invention relates to novel 19,20-didehydro-PG.sub.1 compounds, a disclosure of the preparation and use of which is incorporated here by reference from U.S. Pat. No. 4,228,104.